The oral contraceptive pill has long been the most popular birth control option among women of child-bearing years. However, it increases the risk of dangerous blood clots for some women.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Taking birth control pills that contain the hormone estrogen can increase a risk of blood clotting that can lead to pulmonary embolism (PE).
Knowing the risks can help you decide whether taking the pill makes sense for you.
“Obviously, you have to weigh the risks and benefits of preventing pregnancy with the risk for blood and heart issues,” says vascular medicine specialist Natalie Evans, MD.
“For most young women, it’s not an issue because of their generally low risk of heart and vascular disease. But for those who’ve had blood clots in the past the risk associated with birth control goes up.”
Pulmonary embolism and synthetic estrogen
The most common cause of PE – up to 90 percent of cases – is a blood clot that comes loose in the leg and travels to the lungs.
PE strikes approximately 300,000 people annually. For women taking estrogen-containing birth control, the risk is double.
When produced naturally, estrogen protects women against blood clots, controlling how big clots can grow and speeding up how quickly they can dissolve. However, synthetic estrogen – the form used in oral contraceptives – creates the opposite effect.
Among the general population, only one or two women in 10,000 will develop a blood clot.
Estrogen-containing oral contraceptive pills elevate that risk between twofold and fourfold, says Rebecca Starck, MD, Cleveland Clinic Obstetrics and Gynecology Department Chair. That means the risk increases to at least 1 in 5,000.
It’s important to remember that this increase is still lower than the natural 10-to-15 times risk increase of blood clots that comes with pregnancy.
Risks vary among pill types
Overall, the risk of experiencing PE while taking the birth control pill is low, Dr. Evans says. But some types of pills place you at higher risk.
Studies show that newer progesterone containing OCPs (such as drospirenone) have a higher risk than older generation progesterone containing OCPs. However it is not clear why there is this potential for increased risk.
Is estrogen-containing birth control safe?
While existing research shows estrogen-containing birth control pills do raise the PE risk, there’s still no widespread cause for alarm, Dr. Evans says.
“Most young women are at low risk for blood clots or heart problems. So, even though birth control raises the PE risk, the absolute risk still remains low,” she says. “This just isn’t an issue for most women.”
Doctors should counsel young, healthy women with no history of blood clots and no strong family history of clotting disorders to stop worrying about the risks of hormonal contraception, she says.
Instead, physicians should focus on making sure these women can recognize a blood clot or PE on the rare chance one develops.
Watch for these signs
In some cases, you might not have any symptoms with PE. But if you experience any of these, especially while taking estrogen-containing birth control pills, call 911 or immediately go to the emergency department:
- Sudden coughing, perhaps coughing up blood
- Rapid breathing/shortness of breath
- Severe lightheadedness
You should also be concerned if you notice any signs of a blood clot in your legs. Consult your doctor if you notice:
- Swelling in one or both legs
- Pain/tenderness in one or both legs
- Unusually warm skin on your leg
- Red/discolored skin on your leg
- Veins you can see
Other risk factors
Hereditary blood-clotting conditions can raise the risk as much as 20 times.
Women who smoke while taking an estrogen-containing birth control pill double their risk of experiencing a PE over the increased risk of taking the pill alone, Dr. Starck says.
Several other factors also increase the risk of PE:
- A family history of blood clots
Be aware if you have any increased risk, and if you have questions, talk to your doctor. He or she can recommend birth control medications or devices based on your personal health history.